Raised printing powder and method of making same and using same



3,083,116 RAISED PRINTZNG PDWDER AND METHGD F MAKHQG SAME AND USENG SAME Richard F. Eerndt, North Plainfieid, Ni, assignor to Virkotype Corporation, Piainiield, N..l., a corporation of Virginia No Drawing. Filed Nov. 16, 1959, Ser. No. 852,925 11 Claims. (El. 117-13) This invention relates to raised printing, and particularly to the resin compounds normally employed which may be and are termed raised printing powder. More especially the invention is concerned with a novel colored raised printing powder and the methods by which it may be made.

This application is a continuation-in-part of Serial No. 405,520, filed January 21, 1954, now abandoned.

The raised printing process comprises briefly dusting a powdered resin upon a newly printed sheet, removing therefrom the excess powder which does not adhere to the wet ink, and applying heat to the powder retained on the sheet to fuse it so that particles thereof will flow together and be adhered to the sheet.

initially finely ground and sifted shellac was employed as a powder. Subsequently, however, with the advent of the many synthetic resins now available, synthetic resin compounds became fairly widely used. The shellacs initially employed were bleached and hence transparent, as have been many of the synthetic resin compounds. For coloring of the finished product the color of the ink was initially relied upon. Because of the obvious disadvantages of this manner of coloring, it was not long before attempts were made to color the compounds themselves.

The manner in which the compounds were colored, and in which they are normally colored today, is to incorporate a pigment into a melted batch of the compound. This is then solidified, ground and sifted. This method cannot be easily performed with shellacs, which was early discovered, because of the difiiculty of properly dispersing pigments therein. In Samuel Lipsius Patent No. 1,928,

668 there is disclosed a process for coloring shellac powder which additionally permits the use of unbleached shellac, thereby avoiding the difiiculties inherent in the use of bleached shellac as set forth in the patent. The process of that patent is to coat shellac particles with colored particles.

It has been found, however, that there are numerous limitations and disadvantages in the heretofore available colored raised printing powders and in the methods by which they have been made. Perhaps the most important disadvantage is that full, bright colors having good depth cannot be obtained. This results primarily from the dispersion of the color in the powder particles and hence the weakening of the color. Furthermore, as many pig ments are sensitive to heat, they cannot be used. Thus only heat resistant pigments can be employed, and there fore the choice of colors is small. Another disadvantage is that in order to be economical the powder has to be made in large batches because the subsequent repeat operations of grinding and sifting employed therein leave large residues of fine particle sizes which are not commercially salable and hence must be reused. This results in the necessity for large inventories. Another disadvantage is that if a number of different colored batches of powders are to be made, it is necessary to employ separate grinders, sifters and melting kettles for each color because it is practically impossible to clean the colors from the machines, or at least very costly to do so.

In connection with shellac base powders, the patentee of the aforementioned Patent No. 1,928,668 suggested as indicated that the grains of a shellac powder be coated with color. His only purpose was to permit the use of un- 3,083,116 Fatented Mar. 26, 1963 bleached shellac as a raised printing powder despite its natural orange color. This type of shellac is stable, and hence suitable for use as a raised printing powder, whereas bleached shellac is unsuitable because of its unstableness. While the particle coating methods disclosed in the patent are suitable for the purpose, the product thereof is no better than the conventional colored synthetic resin powder described above. The reasons are obvious, and in fact are suggested by the patentee. Hence in order to get a final color effect, the color of the printing ink must be taken into consideration, as must be the color of the natural shellac. The manufacturer of the powder can accommodate the latter difficulty, but cannot satisfactorily control the former. Also, the colors obtained are not deep and brilliant and, as a matter of fact, are no better than those that would be obtained were the color particles dispersed throughout the shellac particles. In fact, the colors obtained are very comparable to those obtained conventionally by dispersion of color particles in synthetic resin base compounds.

I have discovered that brilliant, full, deep colors that are in no way dependent upon the color of a printing ink employed can be obtained by first dispersing a white pigment throughout each particle of a raised printing powder, which are naturally light in color, and then coating each particle with the desired color. The white base powder forms a background for the surface coated color and prevents dispersion of light through the powder particle, which has heretofore resulted in considerable weakening and lightening of color. Both the synthetic resin type raised printing compounds or powders and the shellac type can now be obtained or can readily be made with a white pigment evenly dispersed therethrough. The manner of accomplishing this dispersion can be that described above, which until now has been currently employed in making heretofore available raised printing compounds. That is, a heat resistant white pigment may be incor porated and thoroughly dispersed in a melted batch of the resinous base material.

There are innumerable satisfactory resin base raised printing compounds. A number, for example, are described in Harnett, Patent No. 2,272,706. Generally they comprise a mixture of thermoplastic resin base, a film former and a plasticizer. A typical formula consists of Part by weight Resin or combination of resins Film former or combination of film formers 17 /2 Plasticizer or combination of plasticizers 17 /2 The resin or resins employed are preferably of the maleic type such as Amberol 801 (Rohm & Haas) or modified Lewisol 2L (Hercules), both maleic modified rosins, or they may be of the phenolic type such as Bakelite BR254 (Bakelite), a paraphenyl phenol resin. All are relatively light in color. A convenient and suitable film former for the first two mentioned resins might be ethyl cellulose. The phenolic resin is the most compatible and the film former employed with it might be ethyl cellulose, cellulose acetate, butyl or vinyl acetate, the acrylics, styrenes, or the like. As a plasticizer any of a number of compounds may be employed such as, for example, Hercolyn hydrogenated methyl abietate Aroclor (chlorinated diphenol) or Santicizer monocresyl diphenyl phosphate.

The above examples should be taken as no more than that, for as indicated, there are innumerable different compounds that may be employed as raised printing powders. In order to make any of the above-specified compositions a white pigmented compound of the type desired, for example 30 parts by Weight of titanium dioxide, may be added to a melted mixture such as that set forth in the preceding paragraph. This is a of titanium dioxide that would be employed as the white pigmenting material would be from about 25 parts by weight to about 30 parts by Weight, as little as 15 parts by weight might possibly be employed and as much-as 49 parts by weight might be employed.

The white pigmented resin is then ground and sifted to various sizes.

According to my invention, a weighed amount of the granular white pigmented base resin, for example of size No. 11 (comparable to US. screen size 120) is placed in a rotating drum. There is then added to the drum a small amount of a groundand finely divided dry pigment, for example, ultramarine blue. The amount of pigment used may for example be .3 of an ounce ,of pigment to a pound of granular resin, though more -or less may be added depending upon the intensity of color sought. The mixture of pigment and granular base resin is then rotated until the pigment is thoroughly and evenly dispersed throughout the granular resin. After this mixing a suitable solvent, for example kerosene or any mineral spirit solvent, if the base resin is of the conventional synthetic type, or an alcohol, for example an isopropyl alcohol, ifzthe base resin material is shellac, is sprayed in small quantity upon the mixture. The amount of solvent which is employed is not critical, but should be only that amount required to soften or tackify the surfaces of the resin particles. Furtherrotation of the drum causes the pigment particles to adhere to the tacky surfaces of the resin particles, thereby resulting in a coating of the latter. The solvent is then evaporated or driven off and the pigment particles are tightly retained upon and partially in the surface portions of the resin particles. T he-resulting product is the novel product of this invention.

When the thus-coated white pigmented resin particles are employed as a raised printing powder, and are fused during the conventional raised printing process, the colored pigment particles carried'on the surface of the resin particles tend to float to the surface of the fused mass, forming a continuous color film. The white pigment-particles remain dispersed through the fused mass, showing through-the color iilmto'a slight extent. Hence the white pigmented particles form a background for the 'color film and lend to it a brilliance of color not heretoforeobtainable.

There are certain pigments which are difficult to disperse in dry mixture because the particles'have a tendency to adhere to one another, thus forming agglomerations. With suchpigments 'I have found that the best dispersion throughout the white pigmented granular-base powder may be achieved by first dispersing or suspending the'pigment in .a liquid vehicle such as water. Whatever the vehicle .chosen, it should be, as is water, a non solvent for the granular base resin powder, and itshould preferably be evaporabie. A number of such pigment dispersionsmay be obtained on the market, for example, flmperial Color Dispersions, manufactured by Imperial Color and Chemical Co., and Auraspers Colors, manufactured by United Wall Paper Co., bothbeing conventional pulp colors dispersed in Water. When employing a .pigment so dispersed or suspended in a liquid vehicle, rather than a dry powdered'pigment, the suspension or dispersion may be added in the same manner as is the finely ground and divided dry pigment in the above example. A After thoroughly mixing it with the granular base resin, however, the mixture should be dried, that is,

achieved if they are added as a suspension. Hence I have found that with Ultramarine blue I achieve best results if it is first suspended in water and then added to the granular white pi gmentcd base resin.

For very pale pastel shades, any type of water soluble dye might be employed in place of the finely ground and divided dry pigment or pigment suspension. The same method would be employed that is employed when using a pigment suspension. Some success has also been achieved by employing a dye that is soluble in the solvent for the base resin material. Hence I have been able to dissolve a suitable .dye in kerosene. This solution was then sprayed into a granular white pigmented base resin mixture and thoroughly mixed. The solvent was then allowed to evaporate. The resulting powder when used gave a pale pastel shade of color.

The attributes of the-new product when employed in a conventional raised printing process are many. The pigments as indicated he on the surface of the fused layers and the white opaque pigment causes a reflection of vivid, bright colors of a depth heretofore unobtainable. As a matterof fact, the surface pigment particles are given an almost fluorescent effect. The surface layer of pigment is normally very thin, and hence the white base color shows through slightly, thereby intensifying the color of the surface pigment. A transparent base coated with the same pigment does not give this same intensity. Rather, the color obtained by coating a transparent base resin is dull and lifeless. Furthermore, using a transparent base material would make it necessary to employ an ink having the same color as is the pigment of the powder, in order that the latter color 'be maintained. With my new powder, however, any color of ink or paper stock may be employed and a true color is obtained. Thus it will now be simple to obtain brilliant color effects at substantially any letter press speed with one impression on any colored paper stock. 7

Various changes and modifications may of course be made in the methods set forth above, without departing from the scope of this invention as set forth in the appended claims. Also, where the term color is employed in the claims, it should be understoodto mean either colored pigments or dye.

I claim:

1. A raised printing powder comprising particles of a resin having white opaque pigment particles disposed through the bodies'thereof, said resinous particles having a surface coating of a differently colored coloring material.

2. A raised printing powder 'as set forth in claim 1 in which the resin is a thermoplastic resin.

3. A raised printing powder as set fort-h in claim .lin which the coloring material is a color pigment.

4. A raised printing powder as set forth in claim 1 in which the resin is a thermoplasticresin and the coloring material is a dye.

5. A raised printing powder as set forthin claim 1 in which the coloring material is a dye.

.6. The process of making a raised printing powder comprising melting a quantity of resin, adding to the melted resin white pigment, dispersing said white pigment throughout the melted resin, solidifying the white pigmerited resin, grinding the solidified resin to form small particles thereof, thoroughly mixing color particles with said White pigmented resin particles, softening the surface-portions of said resin particles with a suitable solvent therefor whereby they become tacky .and said color particles adhere thereto, andevaporating said solventto fix said color particles on said powder particles.

7. The'process according to claim 6 in'which the color particles are dry pigment particles.

8. The process according to claim 6 in which the color particles are dispersed in a liquid vehicle and this dispersion is mixed with the white pigmented resirv particles.

9. The process of claim 6 in which the white pigment is titanium oxide.

10. A method of producing a colored raised printing on a surface which comprises printing the surface with an ink, dusting the surface before said ink dries with a raised printing powder comprising particles of :a resin having white opaque pigment particles dispersed through the bodies thereof, said resinous particles having a surface coating of a differently colored coloring material, removing excess printing powder not adhering to said wet ink, and heating the printing powder adhering to the surface sufficiently to fuse it so that particles thereof will flow together and be adhered to the surface as a raised printing conforming to the design printed on said surface with said ink.

11. A raised printing on a surface comprising a coating adhering to said surface and comprising a resinous mass formed by the heating of a coating of a raised printing 6 powder sufficiently to cause it to fuse and the particles of said printing powder to flow together, said raised printing powder comprising particles of a resin having white opaque pigment particles dispersed through the bodies thereof, said resinous particles having a surface coating of a differently colored coloring material.

References Cited in the file of this patent UNITED STATES PATENTS 1,928,668 Lipsius Oct. 3, 1933 2,272,706 Harnett Feb. 10, 1942 2,497,346 Collins Feb. 14, 1950 2,550,503 Turnbull Apr. 24, 1951 2,758,939 Sugarrnan Aug. 14, 1956 FOREIGN PATENTS 576,389 Germany May 10, 1933 

10. A METHOD OF PRODUCING A COLORED RAISED PRINTING ON A SURFACE WHICH COMPRISES PRINTING THE SURFACE WITH AN INK, DUSTING THE SURFACE BEFORE SAID INK DRIES WITH A RAISED PRINTING POWDER COMPRISING PARTICLES OF A RESIN HAVING WHITE OPAQUE PIGMENT PARTICLES DISPERSED THROUGH THE BODIES THEREOF, SAID RESINOUS PARTICLES HAVING A SURFACE COATING OF A DIFFERENTLY COLORED COLORING MATERIAL, REMOVING EXCESS PRINTING POWDER NOT ADHERING TO SAID WET INK, AND HEATING THE PRINTING POWDER ADHERING TO THE SURFACE SUFFICIENTLY TO FUSE IT SO THAT PARTICLES THEREOF WILL FLOW TOGETHER AND BE ADHERED TO THE SURFACE AS A REISED PRINTING CONFORMING TO THE DESIGN PRINTED ON SAID SURFACE WITH SAID INK. 